Greenhouse trials were conducted to evaluate the effect of treating adult and egg stages of the eastern spruce budworm, Choristoneura fumiferana (Clemens), with Insegar, a water-based commercial formulation of the juvenile hormone analog fenoxycarb, or with water (controls) at droplet sizes and densities comparable to what would be achieved through aerial spraying of field populations. When adult moths were sprayed with the juvenoid at dosages equivalent to 15.5, 155.4, and 310.8 g AI/ha, approximately 90% of the eggs that were subsequently oviposited failed to hatch. The efficacy of the compound (60% suppression of egg hatch) was not as high when the egg stages were sprayed directly at 15.5 and 155.4 g AI/ha. Insegar did not affect the egg productivity of the moths.

A sampling plan for the estimation of the number of achenes damaged by the red sunflower seed weevil, Smicronyx fulvus LeConte, is useful in evaluating the efficiency of weevil management strategies. The objective of this study was to determine the distribution pattern of the damaged achenes that would allow the development of a fixed-sample-size plan for estimation of the damaged achenes. Taylor’s power law and Iwao’s patchiness regression were used to analyze the distribution pattern of the damaged achenes. Slopes from both models were >1, indicating an aggregated spatial pattern. The intercepts and slopes from both models were used to calculate the minimal mean number of damaged achenes per sunflower head that can be estimated for a given sample size and precision level. If the mean number of damaged achenes per head is low (<20), the plan developed using the parameters of Taylor’s power law requires significantly more samples than the plan using the parameters of Iwao’s patchiness regression to estimate the same density of damaged achenes. If the mean number of damaged achenes per head is high (>30), the two plans give similar results. If both low and high damage situations are considered, Taylor’s plan is preferred to Iwao’s plan. At the 0.10 precision level, Taylor’s plan requires approximately 40 samples (heads) to estimate a mean of about 200 damaged achenes per head (≈ current economic injury level).

Because microbial insecticides based on Bacillus thuringiensis subsp. kurstaki cause temporary cessation of larval feeding at sublethal doses, we hypothesized that the delivery of a given dose in a single droplet is more efficacious than delivery of the same dose in multiple smaller droplets. We tested this hypothesis by exposing larvae of the spruce budworm, Choristoneura fumiferana (Clem.), to an LD50 of a commercial product (Dipel 8L) in combinations of droplet sizes and densities that are commonly observed on coniferous foliage after aerial application. A nominal dose of 5.2 International Units (IU) was presented to fifth-instar larvae on one, two, or four balsam fir, Abies balsamea L., needles in the form of one, two, or four droplets with diameters of 84, 66, or 52 μm, respectively. The combinations of droplet size and density were chosen to represent an increasing degree of dose dispersion. Overall mortality after a 24-h exposure was significantly reduced with increasing dose dispersion from an average of 66% when the dose was presented in one 84-μm droplet on one needle to 40% when presented in multiple droplets on several needles. Increased dose dispersion reduced the proportion of larvae that were able to ingest the full dose, presumably because of feeding inhibition caused by ingestion of sublethal droplets. In addition, mortality of fully dosed larvae declined significantly with increasing dispersion, implying a reduction in the effectiveness of the ingested dose. When compared with operational spray deposits, our results suggest that efficacy of spruce budworm sprays may be improved by increasing the proportion of needles receiving a lethal spray deposit by increasing product potency and possibly the active ingredient application rate.

Mixtures of chlorpyrifos and cypermethrin were tested against 1-day-old larvae of corn earworm, Helicoverpa zea (Boddie), and fall armyworm, Spodoptera frugiperda (J.E. Smith), to determine the type of joint action involved in insect mortality. Statistical analyses indicated that mixtures of both insecticides interacted additively in both species. Chlorpyrifos alone was not as effective against larvae of fall armyworm as it was against larvae of corn earworm. No apparent differences in toxicity between the two species were observed with cypermethrin.

Cold treatment is used to control the rusty grain beetle (Cryptolestes ferrugineus) (Coleoptera: Cucujidae), the predominant insect pest of stored grain in Canada. However, because it is difficult to cool the grain enough to control C. ferrugineus quickly, we have examined ways to reduce the cold-tolerance of adult C. ferrugineus, the most cold-hardy stage. We compared the efficacy of two ice nucleators, Pseudomonas syringae and Fusarium avenaceum, to decrease cold-tolerance of this insect, as well as their thermal stability. Ice nuclei from the bacteria P. syringae raised C. ferrugineus supercooling point from −17 to −6 °C, and increased mortality at −9°C for 24 h from 11 to 100%. Pseudomonas syringae held at 30°C for 16 weeks showed only a slight decline in its ability to reduce C. ferrugineus cold-tolerance. The fungus F. avenaceum raised the supercooling point of C. ferrugineus from −17 to −9°C, but only increased the mortality at −9°C for 24 h from 10 to 33%. Wheat treated with F. avenaceum and held at 30°C for 4 weeks reduced the cold-hardiness of C. ferrugineus, but had no effect after 8 weeks at 30°C. One reason for the difference between the two nucleators is that P. syringae had approximately 1000 times more ice nuclei per gram than did F. avenaceum. These results suggest that P. syringae is stable enough to reduce C. ferrugineus cold-tolerance after several weeks on warm grain. We discuss possible ways to increase the ice-nucleating activity of F. avenaceum.

The digestive proteinases of three important pests of canola, Brassica napus L. and B. rapa L., in western Canada were characterized by assessing the proteolytic activity of homogenates of their midguts against azocasein or azoalbumin at various pH levels and in the presence of diagnostic proteinase inhibitors. The midgut of larvae of the bertha armyworm, Mamestra configurata Wlk., had maximum proteolytic activity at pH 10.5 which was inhibited 45–60% by serine proteinase inhibitors such as the soybean trypsin inhibitor. The midgut of larvae of the diamondback moth, Plutella xylostella L., had maximum proteolytic activity at pH 10 which was inhibited 56–75% by serine proteinase inhibitors. The two lepidopterans thus use a serine-like proteinase in digestion. The midgut of adults of the flea beetle, Phyllotreta cruciferae Goeze, exhibited maximum proteolytic activity at pH 5 which was inhibited 33–61% by specific cysteine proteinase inhibitors such as cystatin and trans-epoxysuccinyl-L-leucylamido (4-guanidino)-butane (E-64) and was activated strongly by L-cysteine. Aspartic proteinase inhibitors such as pepstatin A also decreased proteolytic activity by 21–50%. Serine proteinase inhibitors were without effect. Therefore, P. cruciferae appears to use both cysteine- and aspartic-like proteinases in digestion. Cotyledons and first true leaves of canola, B. napus cv. Westar, contained inhibitory activity against serine, cysteine, and aspartic proteinases when tested against bovine trypsin, papain, or porcine pepsin, but the level of antiproteinase activity is insufficient to provide significant resistance against any of these pests.

The discovery of egg masses of Asian gypsy moth onboard Russian freighters in Pacific ports of North America and the capture of adult male gypsy moths in pheromone traps underscored the need for a positive identification of Asian and European gypsy moth males. We have devised a method for differentiation of these two populations based on restriction endonuclease cleavage of a polymerase chain reaction (PCR) generated product. DNA primers for the 5S and 28S rDNA were employed to amplify the ITS2 region using PCR. The ends of the amplified DNA products were sequenced and gypsy moth specific oligonucleotide primers were designed to amplify the gypsy moth ITS2 region. Eleven of 28 restriction enzymes tested cleaved the amplified product. The restriction enzymes ClaI, PvuI, and TaqI generated distinct restriction fragment patterns for the Asian and European gypsy moth PCR product. This diagnostic was applied to samples of field-collected gypsy moths in a double blind test and correctly identified them as Asian or European. Additional studies demonstrated that these primers and restriction enzymes could be used to differentiate among Lymantria dispar, L. monacha, and L. mathura.

Similarities in population parameters among aphid species led us to investigate the potential for a single set of parameters that can be used to develop a ‘generic’ sampling plan for multiple small grain aphid species. A weighted average for the slope and intercept used to relate the proportion of infested tillers to the number of aphids per tiller was determined from the data in 15 published reports. These average parameter estimates were used to predict the number of aphids per tiller in 48 wheat fields sampled for four aphid species. The predicted estimates were regressed on the observed estimates with neither slopes nor intercepts differing significantly from one or zero, respectively. Therefore, it appears the single model is adequate for predicting aphid density for the aphid species tested.

A reliable method for rearing the subterranean summer morph of the sugarbeet root aphid, Pemphigus betae Doane, is described. Field-collected aphids were reared using hydroponic growth pouches that allowed exposed root tissue to be fed on by P. betae. The aphid has been maintained in continuous culture for over 3 years. Open pouches were subsequently modified with cages to provide more successful mass rearing. Cages placed on the pouch were devised to provide an arena that concentrated aphids on one area of the pouch, minimized wandering behavior, and ensured a more vigorous colony. During a 10-week mass rearing experiment, caged pouches consistently averaged 120.8 ± 9.6(se) aphids per cage (fourth instars and adults) following 2-week incubation periods. Caged pouches also were used to isolate individual aphids for development and fecundity studies. Age-specific life tables were developed for P. betae using both open pouches at 20°C, and caged pouches at 24°C. Although the intrinsic rate of increase (rm) was lower at 20°C on a daily time scale (rm = 0.2314 versus 0.2591), rm was significantly greater at 20°C on a degree-day (DD > 7.6°C) time scale (rm = 0.0187 versus 0.0158). The difference on a DD basis resulted primarily from a longer time interval from birth to first reproduction (TFR) at 24°C(TFR = 158.5 versus 147.1 DD at 20°C). These results corroborate previous experience with P. betae, indicating that 20°C appeared to be an optimum temperature for mass rearing. Stable age distributions for P. betae cohorts were only slightly affected by temperature; on average approximately 55, 22, 11, 7, and 5% of the aphids were first, second, third, and fourth instars, and adults, respectively. Though similar studies have not been reported for other Pemphigus spp., all demographic statistics were characteristic of many foliar-feeding aphids held under similar constant temperature conditions.

The objective of this study was to determine the quantitative and seasonal association between the pitch canker fungus, Fusarium subglutinans f. sp. pini, and two potential beetle vectors, Conophthorus radiatae Hopkins and Ernobius punctulatus Fall. In samples of reared and dissected cones, 21.4 ± 2.5% of C. radiatae and 30.1 ± 8.0% of E. punctulatus adults carried propagules of F. s. pini. Seasonal variation in mean percentage of contaminated C. radiatae and E. punctulatus emerged from cones ranged from 0 to 67% and was highest for both species February through April. In sticky traps 12.5 ± 2.3% and 11.8 ± 3.6% of E. punctulatus and Pityophthorus spp., respectively, were contaminated with propagules of F. s. pini.

Conophthorus radiatae and E. punctulatus co-occurred in 26% of the cones. The percentage of cones containing contaminated C. radiatae was greater when E. punctulatus progeny were also contaminated than when E. punctulatus was not. When contamination status of E. punctulatus was not considered, there was no significant difference in C. radiatae contamination between cones with and without E. punctulatus. Because C. radiatae appears to be a vector of the pitch canker fungus, interspecific transmission of inoculum may increase the incidence of this disease.

The parasitoid, Cephalonomia utahensis Brues (Hymenoptera: Bethylidae), was frequently observed parasitizing late-instar larvae of E. punctulatus, but was not found on larvae of C. radiatae. Emergence of large numbers of C. utahensis represents another potential source of inoculum for transmission to prey species.

Four new species are described: Commellus cedilla from Alaska, Canada, and adjacent northeastern states; C. hyphen from the aspen parkland of Saskatchewan to North Dakota; C. semicolon from southern Montana; and Extrusanus oryssus widespread in northern prairies (Alberta to Kentucky). Alary polymorphism in both genera is discussed. Species-specific characters from enclosed male genitalic structures are described and illustrated in detail for the first time, for all species except C. hyphen. Keys are presented to the species of both genera.

Trichogramma minutum Riley entered diapause, in the prepupal stage, in eggs of Lambdina fiscellaria fiscellaria Guenée held at 15°C, 12L:12D, but failed to do so in eggs of Ephestia kuehniella (Zeller), Sitotroga cerealella (Olivier), or Choristoneura fumiferana (Clemens) held under these conditions. The parasitoids emerged without diapause from eggs of all host species held at 25°C, 16L:8D, indicating a role of temperature or photoperiod, or both, in the diapause of the parasitoids in eggs of L. fiscellaria held at 15°C, 12L:12D. Percentage emergence of parasitoids from eggs of L. fiscellaria was virtually the same (>80%) after passing the winter outdoors or after approximately 3 months at 2 °C in the laboratory as it was when reared indoors in this host at 25°C, 16L:8D. Emergence of T. minutum was very poor (<20%) after long-term, low-temperature storage in eggs of C. fumiferana, E. kuehniella, or S. cerealella. Apparently, T. minutum must parasitize diapause host eggs in order to enter diapause, and good survival after long-term low-temperature storage is possible only when T. minutum is in diapause. Trichogramma minutum will enter diapause in L. fiscellaria after 14 days at 15°C, 12L:12D, but the parasitoids need a period of storage at 2°C, 0L:24D for a high percentage of emergence to happen. Over 50% emergence was recorded for T. minutum, held for 300 days in eggs of L. fiscellaria.

The herbivore-resistant synthetic maize BS9 (C4) was grown in three environments, namely, greenhouse with reduced UV light, greenhouse with supplemental UV light, and outside, and leaves at the three-, five-, seven-, nine-, and 10-leaf stages of development were fed to the European corn borer, Ostrinia nubilalis (Hübner). Larvae preferred younger leaves, and leaves grown under reduced UV light, in spite of the high levels of the defence compound 2,4-dihydroxy-7-methoxy-2H-1,4 benzoxazin-3 (4H)-one (DIMBOA). The low level of feeding on leaves from plants grown outside was associated with increased toughness and increased photochemically derived phenolic dimers that cross-link hemicellulose. Tender young maize plants have a low level of cell wall phenolics and depend on a toxin (DIMBOA) for defence. In older plants, DIMBOA levels are low, leaves are tough, and resistance is largely structure-based.

We studied the effects of agricultural practice on ground beetles, using pitfall traps in field plots and in an uncultivated meadow near Edmonton, Alberta. Ground beetle abundance and species richness were higher in plots operated under an organic farming regime than in those under a chemical regime, but neither crop type [barley (Hordeum vulgare L.), faba bean (Vicia faba L.), barley-pea (Pisum sativum L.) intercrop] nor crop rotation had an effect. Reduced tillage did not significantly change overall carabid activity or species richness but species differed in their response to tillage treatments. The carabid assemblage from an uncultivated field differed conspicuously from assemblages in the crops and fescue. Carabid abundance was highest in the meadow and the fauna was dominated by the exotic species Pterostichus melanarius Illiger. Effects of agronomic practice on carabid assemblages are complex, reflecting the interaction of biological traits of particular species and the combination of agronomic treatments applied.

In 1991, a whitefly infestation of unprecedented severity resulted in serious losses of a wide range of food and fiber crops across the southern United States (Perring et al. 1991). Initial indications were that the outbreak consisted of the “type B” or poinsettia strain of the sweetpotato whitefly, Bemisia tabaci (Gennadius). In Canada, B. tabaci was first collected from greenhouse poinsettias in 1988 (Broadbent et al. 1989) and was subsequently found in 18 of 3 1 Ontario greenhouses sampled.